1. Field of the Invention
The present invention relates to a method for flip chip bonding, and more particularly, to a method for flip chip bonding by utilizing an interposer with embedded bumps.
2. Description of the Related Art
FIG. 1 shows a conventional method for flip chip bonding by utilizing an underfill tape with embedded bumps. The conventional method is described as follows. First, a chip 10 having a chip surface 11 is provided. Then, an underfill tape 12 is adhered to the chip surface 11. Then, a plurality of openings 13 are formed on the underfill tape 12 by laser drilling. Then, a plurality of bumps 14 are formed in the opening 13 by plating, wherein the composition of the bumps 14 is 63% by weight of tin and 37% by weight of lead, and the height of the bump 14 is equal to the depth of the opening 13 so that the bump 14 can fill the opening 13 precisely.
Then, a substrate 15 having a substrate surface 16 is provided, wherein the substrate surface 16 has a plurality of pre-solders 17 corresponding to the openings 13. The chip 10 is pressed to the substrate 15 by utilizing a bond head 18, wherein the chip surface 11 faces the substrate surface 16 so that the pre-solders 17 are in contact with the bumps 14. Finally, a reflow step with high temperature (for example, above 200° C.) and high pressure (for example, about 30 Kgm) is applied to the chip 10 and the substrate 15 to fuse the pre-solders 17 and the bumps 14 so as to form a flip chip bonding.
The shortcoming of the conventional method is poor alignment precision. Because the bumps 14 fill the openings 13 precisely, the bottom surface 19 of the underfill tape 12, which is in contact with the pre-solders 17, is a flat surface. Therefore, during the pressing procedure, a sliding movement between the chip 10 and the substrate 15 will cause a shift therebetween, which makes the product defective.
Consequently, there is an existing need for a novel and improved method for flip chip bonding to solve the above-mentioned problem.